MCH is a hypothalamus-derived hormone known to have an appetite increasing action. Furthermore, it has been reported that MCH knockout mouse behaves normally but shows a significantly decreased food ingestion amount and a lighter body weight as compared to normal mouse (non-patent document 1 (Nature, vol. 396, page 670, 1998)). Furthermore, MCH receptor-1-deficient mice have been reported to show a lean phenotype (non-patent document 2 (Proc. Natl. Acad. Sci. USA, vol. 99, page 3240, 2002)). Therefrom MCH receptor (particularly MCH receptor 1) antagonists are expected to be superior appetite suppressants or anti-obesity agents.
As compounds having a MCH receptor antagonistic action, the following compounds are known.
1) Patent document 1 (WO01/21577) discloses a melanin-concentrating hormone antagonist comprising a compound represented by the formula:
whereinAr1 is a cyclic group optionally having substituent(s);X is a spacer with a main chain having an atom number of 1 to 6;Y is a bond or a spacer with a main chain having an atom number of 1 to 6;Ar is a monocyclic aromatic ring optionally condensed with a 4- to 8-membered nonaromatic ring and further optionally having substituent(s);R1 and R2 are the same or different and each is a hydrogen atom or a hydrocarbon group optionally having substituent(s), R1 and R2 may form, together with the adjacent nitrogen atom, nitrogen-containing heterocycle optionally having substituent(s), R2 forms a spiro ring together with Ar, or R2 may form, together with the adjacent nitrogen atom and Y, a nitrogen-containing heterocycle optionally having substituent(s),or a salt thereof.2) Patent document 2 (WO01/82925) discloses a melanin-concentrating hormone antagonist comprising a compound represented by the formula:
whereinAr1 is a cyclic group optionally having substituent(s);X and Y are the same or different and each is a spacer with a main chain having an atom number of 1 to 6;Ar is a condensed polycyclic aromatic ring optionally having substituent(s);R1 and R2 are the same or different and each is a hydrogen atom or a hydrocarbon group optionally having substituent(s), R1 and R2 may form, together with the adjacent nitrogen atom, nitrogen-containing heterocycle optionally having substituent(s), R2 may form, together with the adjacent nitrogen atom and Y, nitrogen-containing heterocycle optionally having substituent(s), or R2 may form, together with the adjacent nitrogen atom, Y and Ar, a nitrogen-containing fused ring optionally having substituent(s),or a salt thereof.3) Patent document 3 (WO03/035624) discloses a compound represented by the formula:
whereinAr is a cyclic group optionally having substituent(s);X is a bond or a spacer with a main chain having an atom number of 1 to 6;R1 and R2 are the same or different and each is a hydrogen atom or a hydrocarbon group optionally having substituent(s),R1 and R2 may form, together with the adjacent nitrogen atom, nitrogen-containing heterocycle optionally having substituent(s);Y is a divalent hydrocarbon group optionally having substituent(s) (excluding CO);R3 is a hydrogen atom or a hydrocarbon group optionally having substituent(s); andring A and ring B may further have substituent(s), and when ring B further has substituent(s), the substituent(s) may be bonded to R1 to form a ring,or a salt thereof or a prodrug thereof.4) Patent document 4 (JP-A-2008-68120) discloses a compound represented by the formula:
whereinR1 is an optionally substituted C1-6 alkoxy group;R2 is a hydrogen atom, a methyl group or a halogen atom;X is a C4-7 hydrocarbon group substituted by a hydroxy group or an oxo group,or a salt thereof.5) Patent document 5 (WO2009/123194) discloses a compound represented by the formula:
whereinring A is a 6-membered ring further optionally substituted;R1 is a hydrogen atom, a halogen atom or a C1-6 alkyl group;R2 is a hydrogen atom or a C1-6 alkyl group;R3 is a group represented by the formula: —Y—S(O)m1—R4a wherein Y is a bond or NH; m1 is an integer of 1 or 2; and R4a is a C1-6 alkyl group optionally substituted by 1 to 3 halogen atoms, or a cyclic group represented by the formula:
wherein m2, m3, m4, n1, n2 and n3 are independently an integer of 1 or 2; and R4b is a C1-6 alkyl group optionally substituted by 1 to 3 halogen atoms (the ring moiety of the cyclic group is optionally further substituted);R5 is a 5- or 6-membered cyclic group optionally further substituted;X1 is a bond or a C1-6 alkylene group; andX2 is a bond or a C1-6 alkylene group,or a salt thereof.6) Patent document 6 (WO2010/087454) discloses a compound represented by the formula:
whereinring A is a tetrahydrofuran ring optionally further substituted;R1 is a hydrogen atom or a halogen atom;R2 is a hydrogen atom, a halogen atom or a C1-6 alkyl group;R3 is a hydrogen atom or a C1-6 alkyl group; andR4 and R5 (1) are each independently a hydrogen atom, an optionally substituted C1-6 alkyl group, an optionally substituted C3-10 cycloalkyl group, or an optionally substituted 5- or 6-membered heterocyclic group, or(2) may form, together with the adjacent nitrogen atom, substituted 4- to 6-membered nitrogen-containing heterocycle,provided thatwhen one of R4 and R5 is a hydrogen atom, then the other is not a group represented by the formula: —X1—RA1 whereinX1 is a bond or a C1-6 alkylene group; andRA1 is a group represented by the formula: —Y—S(O)m1—RB1 wherein Y is a bond or NH; m1 is an integer of 1 or 2; and RB1 is a C1-6 alkyl group optionally substituted by 1 to 3 halogen atoms, or a cyclic group represented by the formula:
wherein m2, m3, m4, n1, n2 and n3 are each independently an integer of 1 or 2; and RB2 is a C1-6 alkyl group optionally substituted by 1 to 3 halogen atoms,(the ring moiety of the cyclic group is optionally further substituted),or a salt thereof.